This invention relates to dispensers in general and more particularly to an improved pump type dispenser which permits dispensing without dribbling.
In the prior art aerosol containers have been used almost exclusively where a fine mist is to be dispensed such as when dispensing perfumes, deodorants, and the like. The recent concern about the pollution of the upper atmosphere by the propellants used in such aerosol containers such as Fluorocarbons and the possibility of legislation prohitibing such propellants has led to the need for improved pump type dispensers which can give performance equivalent to that of of an aerosol.
Small pumps have been used to dispense various materials. A pump exhibiting excellent properties with regard to ease of construction and good sealing to avoid spillage while still having good venting is that disclosed in copending U.S. Application Ser. No. 633,799 now U.S. Pat. No. 4,113,145.
However, a common problem with this and other prior art pumps is that a good dispensing of a fine mist will only take place if the operator pushes down the actuator with the proper force and speed. Otherwise, what is known as dribble occurs, the liquid dribbling out of the outlet instead of coming out in a fine mist. It has been recognized that a solution to this problem lies in preloading the dispenser. Various means have been developed for carrying out such preloading, some of which are described in the aforementioned application. Another example of to preloading device is disclosed in U.S. Pat. No. Re. 28,366 reissued to F. Pechstein on Mar. 18, 1975 based on an original patent issued Nov. 21, 1966. Pechstein's device includes a pump body which has a first, upper variable volume space or cylinder and a lower, second variable volume space. A piston is attached to a stem having an outlet passage which attaches to the actuator nozzle, the piston being disposed within the upper cylinder. A second piston is disposed within the lower cylinder and is biased upward by a spring. Associated with this second piston is a valve. Shown is a ball check valve and a collar valve in two separate embodiments. The stem to which the first piston is attached has a bore formed axially therethrough with the inside end of the bore, which is located within the upper cylinder chamber, closed by a valve. The valve is attached to the second piston in a manner such that there is the possibility of relative motion between the valve and the second piston. In the illustrated embodiment this is accomplished through the use of fingers on a shaft extending from the second piston and riding in slots formed in a depending portion of the valve member. In operation, as explained in the patent, pressing down on the actuator causes downward movement of the second piston compressing the spring which is biasing it upward. The piston moves downward with the fingers riding in the slots until a certain predetermined precompression is obtained whereupon the valve to the outlet passage in the stem is opened by further movement of the second piston permitting material to be dispensed therethrough and out of the nozzle actuator.
As can be seen from the above description, the pump comprises a relatively large number of parts. These include the pump housing, the stem and first piston, the valve at the inlet to the axial outlet bore in the stem, the connecting member between the second piston with its fingers, the ball check valve, the second piston and the spring. In the one embodiment utilizing a resilient collar, the number of parts is reduced since it is possible to make the second piston, valve and connecting means of the single part. However, the difficulty in inserting this connecting member into the valve so that the the pins are free to slide in slots therein, possibly requiring a separate pin press fitted into the connecting member, is evident. In pumps of this nature which are to be used with throw-away dispensers the cost of making the pump is significant. Even a difference in cost only amounting to pennies can make the difference between a successful and unsuccessful product. Thus, the large number of parts in this device is problematic, particularly because of the increased cost of assembly which would be involved.
Another pump of somewhat similar construction is known. In this pump upper and lower pistons are used as in the above patent. Once again a valve is used for closing off an axial passage or bore through the stem which is connected to the upper passage. A lower piston which is closed off by a ball check valve is utilized with a connecting member extending therefrom and rigidly connected to the valve at the bottom of the axial passage. This pump includes a spring, a body member, an upper piston and stem assembly, a valve and connecting member assembly, and the lower piston assembly, which snaps into the valve and connecting member assembly after a ball check valve is placed in a suitable recess therein. Thus, this valve too, although presently being produced and used, requires additional assembly steps over conventional pumps.
In view of the above discussion the need for an improved pump which fulfills the purpose of prepressurization to permit dispensing a material in a fine mist regardless of how quickly the user presses the actuator button, which pump can be made in a inexpensive and simple manner with a minimum number of parts becomes evident.